Installed new carbs, now have flames shooting out the exhaust!

[Dean...]

Hoping to get some help before I start working on my car tomorrow after work..

The engine is a 1916 in good condition. Tappets were set a couple weeks ago when the pushrod tubes were replaced. It has a brand new CB Performance Magnaspark 2 distributor and accompanying coil.

The engine lid used to have stand offs. A couple months ago I was out of action due to a work injury and the car didn't get much use at that time. We had heaps of rain and the rain went down the carbs. Got all that sorted, and rather than the mechanic rebuild the carbs on the car which were copies of 44 Webers with 28mm Venturis, he rebuilt a set of genuine 40's that I had which had a 35mm Venturis. When these carbs were on the car, it ran like a scolded cat, but over time they started leaking in the shaft and I stripped them down and fixed this issue, but after reinstalling them I went to some performance mechanic who said he couldn't set the idles because they were seized. So to make life easier I bought three copies from a reputable guy in Australia, his name is Rod Penrose.

Anyways, after this mechanic rebuild the fancy Webers and did everything else, he finally got it going, but not great. I expected the same 'thrown back into the seat' performance like it used to be, but it just wasn't there. After a couple weeks, it was running worse and worse so I decided I needed to give the 44's a good clean and put them back on.

While doing this, I found one nut on each inlet manifold lose where they mount to the head, one was only finger tight and the gasket was still soaking wet from when I was trying to find air leaks. I wanted the power up top again so when I cleaned up these copies I installed 34mm vents, 1mm smaller than what was on the original Webers. I then cleaned up good the main jets that were in the original Webers used them. I've adjusted the idle mixture, and can get the engine to idle at around 500, but I know that's probably a little too slow so I'll fix that tomorrow. What I didn't do, is play around to much with the linkages. I set the rods so they come off idle at the same time, but that's it.

I can't drive it over 3000rpm. The more I try to accelerate, the worse it is and wants to stop. I thought it could have been the main jet size, because I first used what was originally in The copies, which were 125, but when I pulled the jets out of the real Webers, they too were stamped 125. Then it got me thinking that they may have been drilled, and that's why I decided to try them.

The timing is probably a little retarded, but not likely to much. I seem to be able to rev it in the driveway, which is when I see the flames, so it's quite possible that I got the engine to rev around 3500 and set it to 32.

The spark plugs are all coming and going to the right place. The auto parts place didn't have the right plugs, I had to actually buy a set that were one stage cooler. I also set the gaps to 0.9mm if I remember correctly, which is what come up when I Googled.

I'm fine with spending the time to get the linkages right as I always knew I had to do them, but I didn't won't to do them tomorrow, thinking that it will fix the issue when you guys think the problem is more likely something else, so I appreciate any help I can get.

And if anyone can suggest a good spring setup for the distributor, that would be cool too!

Thanks in advance everyone!
Cheers
Dean

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[Dean...]

Anyone have any thoughts? I have the day off work tomorrow, so will be spending it working on the car. I'm keen to hear from people who know what they are doing

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[Ol'fogasaurus]

What do the spark plugs look like when you pull them? Look for a difference between sides and/or front to rear. The plugs heat range potentially could be off but I wouldn't think is would be that bad. The drilling of the jets might show up there as well as some other things.

Check the high tension lead from the coil to the dist. The other day we were trying to solve a problem and when checking the plug wires with a volt OHM meter the condition of the plug wires caused the meter to slam the side but not so the high tension lead. We did the same thing with our back up high tension lead that had been sitting around unused for a long time; when testing it the needle of the volt OHM meter didn't even move. Replacing it with a new one made a big difference although we think on of the carbs still might have an issue.

If there was a manifold or carb seal problem (loose nuts) as you said and the carbs were synced with this problem then you might have a problem there.

What Distributer are you using? Even with the stock VW units, not all are the same or of the same quality as others, for example: with the manual advance 009s; some are good while others aren't (cast vs. stamped bodies for example). I sure would have the dist. checked for condition and advance characteristics then recheck the timing.

More info: Backfiring through the carb is usually timing or lean carburation. Back firing through the mufflers is normally a rich condition but flames out the tail pipe usually means that fuel or fuel vapors are collecting in the muffler and then igniting due to timing or... you have installed one of those kits that allow you to do the tail pipe flame job like what is shown in the movie "Grease". Some of the how to shows on TV have shown how to do it. Probably not legal either .

[Dean...]

Thanks heaps for your reply!

All the leads are brand new, and came with the CB Performance Magnaspark 2 distributor which also came with a new coil. The distributor is setup in the way it arrived.

Your suggestion about the linkages could be on the money, but I did notice at first when the other carbs were installed and the linkages set, that it did run ok, it was over time that they got worse which could be because gradually the nuts come loose.

I've come up with possible cause which I really hope is not true.... With the nuts coming loose on the inlet and causing the mixture to be lean, maybe I now have at least one burnt out valve which is letting fuel into the exhaust and causing the fire... Anyways I'm going to buy what I know to be 145 jets and get the carbs idling well before I play with the linkages.

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[Ol'fogasaurus]

A burnt or hung up valve is an easy find doing a compression test which I recommend when anyone gets a new toy. Also, on a new engine after the first startup and break in run.

Even a hand over and slightly back of the tail pipe you can notice a miss in the exhaust; sniff your hand to see if you get a strong gas or oil smell also. A clean piece of paper in the same way can tell one sometimes if the rings or seals are going on you buy the soot on the paper. Old tricks.

Yes, the linkage disparity between the two carbs can occur when a locking nut comes loose.

Sounds like you have a good starting plan.

[Dean...]

Thanks for the tips!

Unfortunately I still have the problem. I replaced the main and idle jets, so I doubt they are the culprit. Timing is fine, and I even removed the Magnaspark and reinstalled the old ignition setup. I gapped The plugs at 028. No matter what I've done, I'm getting flames out the exhaust.

While I was at it I adjusted the Bowden tube and it looks like cylinder 3 may have seen a lot of heat going by the jtube.

I'm going to have to get myself a compression tester. I cut holes so I can better get to the plugs today, so that will help with doing the test.

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[Dean...]

I bought the compression tester, but had other stuff to do at home. I have taken pics of the plugs that are less than an hour old; I bought them and installed them when I first installed the 44 Webers and when I noticed I had the flames. They were gapped at 040.

The pics are in order. The first is of plugs one and two, the next pic is 3 and 4.

I'm going to try and do the compression test after work tomorrow, because I really do need it back on the road. [IMG]//uploads.tapatalk-cdn.com/201707 ... 4553b2.jpg[/IMG][IMG]//uploads.tapatalk-cdn.com/201707 ... e424b9.jpg[/IMG]

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[Dean...]

Plugs 1 to 4 from left to right[IMG]//uploads.tapatalk-cdn.com/201707 ... 5a06bc.jpg[/IMG]

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[Dean...]

I just had a thought..... I've had the car for about 18 months and it was only just a couple weeks ago when I was getting it ready for rego, that I found the fuel filter. I don't suppose a blocked fuel filter will cause my issues? I'm guessing that it's possible that if it's blocked it could cause the motor to run like crap when revving it high, but I'm not sure how it would cause the flames, unless there isn't enough fuel in each cylinder to be of use, so a lot of what isn't burnt goes into the exhaust and that's where it catches on fire. Possible? Anyways, just sharing my thoughts, I'll try and make sure I do the compression test tomorrow.

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[Ol'fogasaurus]

With the black soot they look kind of... Here, this should help: http://www.verrill.com/moto/sellingguid ... rchart.htm

[SCOTTRODS]

The plugs don't look oil fouled... that's a plus. But the #3 looks excessively rich... and the rest a little rich. Usually #3 is the one that runs hot and will have a whiter appearance than the rest from Shade tree mechanics... Since it looks rich, that's a fuel issue to figure out, could be poor valve adjustment, could be carb adjustment (I'll go with carb on this one form all the other entries).... when you said there were flames from the exhaust that said "rich" as well. I suppose it could be a valve bent or sticking too... but generally that's not the first place I go... It makes a mess to find that one usually, but I will often pull the valve covers and remove the spark plugs after a warm up and turn the engine using the Starter to physically watch for sticking valves... Trust me... you can see them if they don't move at Starter spin rates. Don't wait til it cools at all to use this approach... cooling may change things and make it better... OR if your issue is when cold, let it cool before doing this "test". But for now, Yes... you have a Rich condition... Those plugs should have a slightly tan appearance or slightly grey... but look mostly new other than that... all of them look "sooty".

[Dean...]

Thanks heaps for the advice!

I think the plugs look the way they do because I put them in, then warmed up the engine for a while while the carbs were at their initial settings, and then adjusted the idle once warm. Then I went for a drive around the block and that's when I stopped and noticed the flames, so they're probably sooty from the warm up and adjustment time the engine was running.

Tomorrow I hope to do the compression test and I'll do as suggested and take the tappet covers off and look for a bad valve.

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[Ol'fogasaurus]

Dean, I think they are too sooty for just a startup, warm up then adjustment. You could be suffering anything from jets to float adjustment to stuck floats (including debris [fuel filter missing]) to almost anything.

I am assuming that it ran OK before going to the 44 Webbers, is that right?

[Dean...]

I installed the 44's because the engine was running really bad to the point I couldn't drive it. It was backfiring all the time and scaring pedestrians lol

It was in that process that I found that the mechanic who has worked on it a couple weeks prior, had not done the manifold bolts up properly, with number 3 not even requiring tools to remove as it was so loose, and number 1 was almost the same.

It was because of how poorly the engine was running that I swapped carbs. These carbs used to be on the engine and it always ran well, but before installing them again, and went right through them and gave them a good clean up. I didn't do anything with the float level, because it was always fine before. The only change I initially made was I swapped the 28mm Venturi for 34mm, and when those plugs were in the engine, it was running the same jets as it had when the 28mm Venturis were in it, so if anything it should have been running lean. The other day I swapped the jets with brand new ones; 52 idles changed to 55, and 125 mains to 145.

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[SCOTTRODS]

are your air filters dirty as hell or something simple??? You don't just start having these problems without a cause... so I'm still looking at running rich for some reason also.

I work on a ton of smaller engines and get to troubleshoot by all kinds of means. Recently, I had an engine swap to do from an engine running lean, that was scorched cylinders... (this one was only 36 hp) to a new exact model except the intake was different since they don't make the same intake any longer... Changed the intake (all prior to carb) from the old engine... hey, they guy had been running it for almost a year like that... and couldn't get the damn thing to run right... One time I'd pull the plugs after a short run (Less than 2 minutes even sometimes) and I'd find plugs that showed Lean condition... make a few changes and try again and the SAME pugs would come out sooty like yours... Pull the air filter off and run it again... Lean as hell with white plugs again... This is a Briggs large bore tin cylinder v-twin, but an engine is an engine especially where air cooled is involved, in my experience... I talked to Briggs Technical support and about 25 other "experts" in and out of the business I work at and no one could figure this out... I just kept the machine sitting on the back burner and kept trying everything I knew including jets and float and all that crap... every time I talked to everyone, I told them about the intake change and the other bits of info and no one could identify this anomaly... until one day a newb comes in and is tinkering with it after I went home and he accidentally bumped the choke when he was moving his hand from the throttle. The next morning he demonstrated the accident with repeatable results and eventually that intake was found to be the problem... Just an adapter for a different kind of air filter was all it was... but inside it there was a little hump designed in the throat, that was interrupting the air flow in the wrong place for the venturi to flow fuel properly... most times it was causing too much of a pressure drop and flooding it, other times it was causing to little pressure drop and all of it due to the location of the hump, coupled with the position of the choke being very slightly different... I usually (just like on that motor) pull the choke through a few times looking for a sweet spot to show up like that, but it never happened for me. The newb just happened to hit the right spot and realized where it was and could repeat it... IN this case, I put the intake that came with the engine back on it, and never had another issue. I had to modify the hell out of the machine frame and body to make it work and it left the air filter assembly sticking up 6 inches higher than the machine, but sometimes ya have to do what has to be done. The engine that was pulled in this machine died of the same cause we were experiencing, so we have no idea how he managed to use it like that for over a year... but he somehow did...

So the moral of the story is: sometime just back tracking to the point where it was when it started having issues might not be such a bad idea... But the road to the discovery can be hard and time consuming.

Hope you figure out the issue... it sounds very frustrating.